1. Field of the Invention
The present invention relates to a negative electrode for rechargeable lithium batteries and rechargeable lithium batteries including the same.
2. Description of the Related Art
Lithium rechargeable batteries have recently drawn attention as power sources for small portable electronic devices. Lithium batteries use organic electrolyte solutions, thereby have a discharge voltage that is twice as high as conventional batteries using alkali aqueous solutions. Accordingly, lithium rechargeable batteries have high energy density.
Lithium-transition element composite oxides capable of intercalating lithium, such as LiCoO2, LiMn2O4, LiNi1-xCoxO2 (where, 0<x<1), and so on, have been researched as positive active materials for rechargeable lithium batteries.
Various carbon-based materials that can intercalate and deintercalate lithium ions such as artificial graphite, natural graphite, and hard carbon have been used as negative materials. Graphite increases the discharge voltage and energy density of a battery because it has a low discharge potential compared to lithium (e.g., 0.2V).
Batteries using graphite as a negative active material have a high average discharge potential (e.g., 3.6V). In addition, graphite is more commonly used among the aforementioned carbon-based materials since graphite imparts a better cycle life due to its reversibility characteristic. However, graphite has low density and consequently, low capacity in terms of energy per unit volume when it is used as a negative active material. Further, it can create swelling or capacity reduction when it reacts with an organic electrolyte at a high discharge voltage.
Other materials, such as oxides, or more particularly tin oxide, lithium vanadium-based oxide, and the like have been proposed. However, the use of such oxides for negative electrodes has not shown sufficient improvements in battery performance, and therefore, further research in oxide negative materials continues to develop.